Efficient uplink feedback in a wireless communication system

ABSTRACT

A method for transmitting control information by transmitting a reference signal from a first transceiver to a second transceiver, in response to the reception of the reference signal, determining at the second transceiver a plurality of control channel elements based upon the received reference signal, jointly encoding the plurality of control channel elements at the second transceiver to generate a control signal, and transmitting the control signal from the second transceiver to the first transceiver.

CLAIM OF PRIORITY

This application makes reference to, incorporates the same herein, andclaims all benefits accruing under 35 U.S.C.§119 from a provisionalapplication earlier filed in the U.S. Patent & Trademark Office on 21Mar. 2007 and there duly assigned Ser. No. 60/919,311.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for control channeltransmission in a wireless communication system, and more specifically,a method for coding and mapping control channel information in awireless communication system.

2. Description of the Related Art

Orthogonal Frequency Division Multiplexing (OFDM) is a popular wirelesscommunication technology to multiplex data in frequency domain.

In a communication system, a multi-path communication channel results ina frequency-selective fading. Moreover, in a mobile wirelessenvironment, the channel also results in a time-varying fading.Therefore, in a wireless mobile system employing OFDM, the overallsystem performance and efficiency can be improved by using, in additionto time-domain scheduling, frequency-selective multi-user scheduling. Incase of frequency-selective multi-user scheduling, a contiguous set ofsubcarriers potentially experiencing an upfade is allocated fortransmission to a user. Upfade is a situation where multipath conditionscause a radio signal to gain strength. The total bandwidth is dividedinto multiple subbands, and each subband contains multiple contiguoussubcarriers.

A multiple antenna communication system, which is often referred to asmultiple input multiple output (MIMO) system, is widely used incombination with OFDM technology, in a wireless communication system toimprove system performance.

In a MIMO system, both transmitter and receiver are equipped withmultiple antennas. Therefore, the transmitter is capable of transmittingindependent data streams simultaneously in the same frequency band.Unlike traditional means of increasing throughput (i.e., the amount ofdata transmitted per time unit) by increasing bandwidth or increasingoverall transmit power, MIMO technology increases the spectralefficiency of a wireless communication system by exploiting theadditional dimension of freedom in the space domain due to multipleantennas. Therefore MIMO technology can significantly increase thethroughput and range of the system.

When the transmission channels between the transmitters and thereceivers are relatively constant, it is possible to use a closed-loopMIMO scheme to further improve system performance. In a closed-loop MIMOsystem, the receiver informs the transmitter of feedback informationregarding the channel condition. The transmitter utilizes this feedbackinformation, together with other considerations such as schedulingpriority, data and resource availability, to optimize the transmissionscheme.

A popular closed-loop MIMO scheme is MIMO precoding. With precoding, thedata streams to be transmitted are precoded, i.e., pre-multiplied by aprecoding matrix, before being passed on to the multiple transmitantennas in a transmitter.

In a contemporary closed-loop MIMO precoding scheme, when a transmitterprecodes data before transmitting the data to a receiver, thetransmitter informs the receiver of the precoding information such as anidentification of the precoding matrix by transmitting explicit controlinformation that carries the precoding information. A significantproblem with this approach is that the control information inefficientlyconsumes a significant amount of system resources and degrades theoverall system throughput and capacity.

In packet-based wireless data communication systems, a so-called controlchannel usually accompanies the data transmission. In the thirdGeneration Long Term Evolution (3G LTE) system, the control channel thatcarries the control signal is referred to as Physical Downlink ControlChannel (PDCCH) for transmission from a base station to a unit of userequipment, or Physical Uplink Control Channel (PUCCH) for transmissionfrom a unit of user equipment to a base station. The PDCCH carriesinformation such as user equipment (UE) ID, resource assignmentinformation, Payload size, modulation, Hybrid Automatic Repeat-reQuest(ARQ) HARQ information, MIMO related information. A Cyclic Redundancycheck calculated over the control information and masked by the UE IDcan be carrier instead of explicit UE ID.

The different types of feedback information from the UE carried in PUCCHare summarized below:

Subbands CQI Information

MIMO Rank

Antenna/Layer selection

MIMO Precoding

ACK/NACK for downlink data transmission

Contemporarily, each type of feedback control information is separatelycoded or modulated and transmitted. This results in inefficienttransmission because efficient coding across multiple control typescannot be employed. Moreover, if some type of CRC is used for errordetection purposes, separate CRCs are required for each of the controlinformation types resulting in excessive overhead.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide animproved method and apparatus for transmission of control channelinformation.

It is another object of the present invention to provide an improvedmethod and apparatus for control channel transmission to efficientlyutilize transmission resources.

According to one aspect of the present invention, a method fortransmitting control channel information may include transmitting areference signal from a first transceiver to a second transceiver; inresponse to the reception of the reference signal, determining at thesecond transceiver a plurality of control channel elements based uponthe received reference signal; jointly encoding the plurality of controlchannel elements at the second transceiver to generate a control signal;and transmitting the control signal from the second transceiver to thefirst transceiver.

The plurality of control channel elements may include a subband channelquality indicator, an indicator for multiple input and multiple outputrank and selected layers, an indicator for multiple input and multipleoutput precoding, an indicator for acknowledgement or negativeacknowledgement, and an indicator for cyclic redundancy check.

When four antennas are used by the first transceiver, the indicator formultiple input and multiple output rank and selected layers may beformed with four bits. When two antennas are used by the firsttransceiver, the indicator for multiple input and multiple output rankand selected layers may carry two bits.

The method may further include presetting an indicator for multipleinput and multiple output rank and selected layers . In this case, theplurality of control channel elements may include a subbands channelquality indicator, a format indicator, an indicator for multiple inputand multiple output precoding, an indicator for acknowledgement ornegative acknowledgement, and a cyclic redundancy check indicator.

The method may further include presetting an indicator for multipleinput and multiple output precoding. In this case, the plurality ofcontrol channel elements may include a subbands channel qualityindicator, a format indicator, an indicator for multiple input andmultiple output rank and selected layers, an indicator foracknowledgement or negative acknowledgement, and a cyclic redundancycheck indicator.

The method may further include presetting a subbands channel qualityindicator. In this case, the plurality of control channel elements mayinclude a format indicator, an indicator for multiple input and multipleoutput rank and selected layers, an indicator for multiple input andmultiple output precoding, an indicator for acknowledgement or negativeacknowledgement, and a cyclic redundancy check indicator.

The plurality of control channel elements may be jointly encoded byinserting a selected set of tail bits into the plurality of controlchannel elements; encoding the tail bits inserted control channelelements using a selected code; puncturing the encoded control channelelements; modulating the punctured control channel elements to generateda plurality of equal-. length modulated symbols using a selectedmodulation scheme; modulating a selected sequence using the modulatedsymbols to generated a plurality of modulated sequences; mapping theplurality of modulated sequences into available transmission resources;and converting the mapped symbols to radio frequency signals.

The selected code may be one selected from a group comprisingconvolutional codes, tail-biting convolutional codes and block codes.

The selected modulation scheme may be one selected from a groupcomprising Quadrature Phase-Shift Keying (QPSK), Binary Phase ShiftKeying (BPSK), and Quadrature Amplitude Modulation (QAM).

Each of the modulated sequences may be a Constant Amplitude ZeroAutoCorrelation (CAZAC) sequence.

The plurality of modulated sequences may be mapped into the availabletransmission resources by dividing the available transmission resourcesinto a plurality of equal duration resource elements in time andfrequency domain, with each resource element formed with a plurality ofsubcarriers, and the number of subcarriers in each resource elementbeing equal to the length of each of the plurality of modulatedsequences; selecting two sets of resource elements in a time-domainsubframe for control channel transmission, with the number of resourceelements in the two sets of resource elements being equal to the numberof the plurality of modulated sequences, with a first set of resourceelements being located in one edge of the subframe in time and frequencydomain, and a second set of resource elements being located in theopposite edge of the subframe in time and frequency domain; and mappingthe plurality of modulated sequences into the two sets of resourceelements.

The plurality of modulated sequences may be mapped into the availabletransmission resources by dividing the available transmission resourcesinto a plurality of equal duration resource elements in time andfrequency domain, with each resource element formed with a plurality ofsubcarriers, and the number of subcarriers in each resource elementbeing equal to the length of each of the plurality of modulatedsequences; selecting a plurality of continuous time-domain subframes forcontrol channel transmission, selecting two sets of resource elements ineach time-domain subframe, with a first set of resource elements beinglocated in one edge of the subframe in time and frequency domain, and asecond set of resource elements being located in the opposite edge ofthe subframe in time and frequency domain, and the relationship betweenthe number of resource elements in the two sets of resource elements ineach selected subframe the number of the plurality of modulatedsequences being established by:

M=X×N

where M is the number of the modulated sequences, X is the number of theselected subframe, and N is the number of resource elements in the twosets of resource elements is each selected subframe; and mapping theplurality of modulated sequences into the selected resource elements inthe selected subframes.

The plurality of modulated sequences may be mapped into the availabletransmission resources by dividing the available transmission resourcesinto a plurality of equal duration resource elements in time andfrequency domain, with each resource element formed with Y subcarriers,the length of each of the plurality of modulated sequences being Z, andY/Z=B, where B is a positive integer; selecting two sets of resourceelements in a time-domain subframe for control channel transmission, thenumber of resource elements in the two sets of resource elements equalsto the number of the plurality of modulated sequences, with a first setof resource elements being located in one edge of the subframe in timeand frequency domain, and a second set of resource elements beinglocated in the opposite edge of the subframe in time and frequencydomain; and mapping the plurality of modulated sequences into the twosets of resource elements, with each resource element corresponding to Bmodulated sequences.

Alternatively, the plurality of control channel elements may be jointlyencoded by inserting a selected set of tail bits into the plurality ofcontrol channel elements; encoding the tail bits inserted controlchannel elements using a selected code; puncturing the encoded controlchannel elements; modulating the punctured control channel elements togenerated a plurality of equal-length modulated symbols using a selectedmodulation scheme; mapping the plurality of modulated symbols intoavailable transmission resources; and converting the mapped symbols toradio frequency signals.

The plurality of modulated symbols may be mapped into the availabletransmission resources by dividing the available transmission resourcesinto a plurality of equal duration resource elements in time andfrequency domain, with each resource element corresponding to onesubcarrier; selecting two sets of resource elements in a time-domainsubframe for control channel transmission, with a first set of resourceelements being located in one edge of the subframe in time and frequencydomain, and a second set of resource elements being located in theopposite edge of the subframe in time and frequency domain, and thenumber of resource elements in the two sets of resource elements in thesubframe equals to the number of the plurality of modulated symbols; andmapping the plurality of modulated symbols into the two sets of resourceelements.

According to another aspect of the present invention, a transmitter maybe constructed with a control information generator that generates aplurality of control elements; a tail bit insertion unit that inserts aselected set of tail bits into the plurality of control channelelements; a coding unit that encodes the control channel elements usinga selected code; a puncturing unit that punctures the encoded controlchannel elements; a first modulator that modulates the punctured controlchannel elements to generated a plurality of modulated symbols using aselected modulation scheme; a mapping unit that maps the plurality ofcontrol elements into available transmission resources; a upconversionunit that converts the mapped symbols to radio frequency signals; atleast one antenna coupled to transmit the radio frequency signals.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention, and many of the attendantadvantages thereof, will be readily apparent as the same becomes betterunderstood by reference to the following detailed description whenconsidered in conjunction with the accompanying. drawings in which likereference symbols indicate the same or similar components, wherein:

FIG. 1 is an illustration of an Orthogonal Frequency DivisionMultiplexing (OFDM) transceiver chain suitable for the practice of theprinciples of the present invention;

FIG. 2 is a block diagram of a transmitter and a receiver for a discreetFourier transform (DFT) spread orthogonal frequency divisionmultiplexing system;

FIG. 3 illustrates a subcarrier allocation scheme forfrequency-selective multi-user scheduling and frequency diversity in anOFDM system;

FIG. 4 illustrates an example of frequency-selective scheduling in anOFDM system;

FIG. 5 is an illustration of a multiple input multiple output (MIMO)system suitable for the practice of the principles of the presentinvention;

FIG. 6 is an illustration of a single-code word MIMO scheme suitable forthe practice of the principles of the present invention;

FIG. 7 is an illustration of a multi-code word MIMO scheme suitable forthe practice of the principles of the present invention;

FIG. 8A and FIG. 8B are examples of precoding in a precoding MIMO-systemsuitable for the practice of the principles of the present invention;

FIG. 9 is an illustration of an example of MIMO precoding on differentsubbands suitable for the practice of the principles of the presentinvention;

FIG. 10 is an illustration of an example of MIMO rank on differentsubbands suitable for the practice of the principles of the presentinvention;

FIG. 11 is an illustration of an example of MIMO layer ordering ondifferent subbands for a 2×2 MIMO system suitable for the practice ofthe principles of the present invention;

FIG. 12 is an illustration of single carrier frequency division multipleaccess (SC-FDMA) transceiver chain;

FIG. 13 is a resource allocation scheme for control channel in a SC-FDMAsystem;

FIG. 14 illustrates a method for jointly encoding feedback informationaccording to a first embodiment of the principles of the presentinvention;

FIG. 15 illustrates an example of rank and selected layers indicator forfour-transmission antennas case;

FIG. 16 illustrates a method for jointly encoding feedback informationaccording to a second embodiment of the principles of the presentinvention;

FIG. 17 illustrates a detailed example for jointly encoding feedbackinformation according to the second embodiment of the principles of thepresent invention;

FIG. 18 illustrates a method for mapping control channel informationinto transmission resources according to a third embodiment of theprinciples of the present invention;

FIG. 19 illustrates a method for coherent transmission and a method ofcoherent reception;

FIG. 20 illustrates a method for mapping control channel informationinto transmission resources according to a fourth embodiment of theprinciples of the present invention;

FIG. 21 illustrates a method for mapping control channel informationinto transmission resources according to a fifth embodiment of theprinciples of the present invention;

FIG. 22 illustrates a method for mapping control channel informationinto transmission resources according to a sixth embodiment of theprinciples of the present invention;

FIG. 23 illustrates a method for mapping control channel informationinto transmission resources according to a seventh embodiment of theprinciples of the present invention;

FIG. 24 illustrates a method for non-coherent transmission and a methodof non-coherent reception; and

FIG. 25 illustrates a method for mapping control channel informationinto transmission resources according to an eighth embodiment of theprinciples of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates an Orthogonal Frequency Division Multiplexing (OFDM)transceiver chain. In a communication system using OFDM technology, attransmitter chain 110, control signals or data 111 is modulated bymodulator 112 and is serial-to-parallel converted by Serial/Parallel(SIP) converter 113. Inverse Fast Fourier Transform (IFFT) unit 114 isused to transfer the signal from frequency domain to time domain. Cyclicprefix (CP) or zero prefix (ZP) is added to each OFDM symbol by CPinsertion unit 116 to avoid or mitigate the impact due to multipathfading. Consequently, the signal is transmitted by transmitter (Tx)front end processing unit 117, such as an antenna (not shown), oralternatively, by fixed wire or cable. At receiver chain 120, assumingperfect time and frequency synchronization are achieved, the signalreceived by receiver (Rx) front end processing unit 121 is processed byCP removal unit 122. Fast Fourier Transform (FFT) unit 124 transfers thereceived signal from time domain to frequency domain for furtherprocessing.

The total bandwidth in an OFDM system is divided into narrowbandfrequency units called subcarriers. The number of subcarriers is equalto the FFT/IFFT size N used in the system. In general, the number ofsubcarriers used for data is less than N because some subcarriers at theedge of the frequency spectrum are reserved as guard subcarriers. Ingeneral, no information is transmitted on guard subcarriers.

In a DFT-spread OFDM system, the data to be transmitted is firstmodulated by a QAM Modulator 131. The QAM modulated symbols areFFT-pre-coded by a FFT unit 133 before mapping into IFFT unit 135 asshown in FIG. 2. The subsequent signal processing is similar to thetransmitter in the example as shown in FIG. 1, and thus the explanationthereof is omitted. At the receiver, the received signal is processedsimilarly as in the receiver shown in FIG. 1 until the FFT operation byFFT unit 143. Frequency-domain equalization (FDE) is performed by a FDEunit 145 after the FFT operation. An IFFT operation is then performed byIFFT unit 147 on the equalized symbols in order to obtain the datamodulated symbols.

In a communication link, a multi-path communication channel results in afrequency-selective fading. Moreover, in a mobile wireless environment,the channel also results in a time-varying fading. Therefore, in awireless mobile system employing OFDM/DFT-Spread-OFDM based access, theoverall system performance and efficiency can be improved by using, inaddition to time-domain scheduling, frequency-selective multi-userscheduling. In case of frequency-selective multi-user scheduling, acontiguous set of subcarriers potentially experiencing an upfade isallocated for transmission to a user. Upfade is a situation wheremultipath conditions cause a radio signal to gain strength. The totalbandwidth is divided into multiple subbands, and each subband containsmultiple contiguous subcarriers. As shown in FIG. 3, subcarriers f₁, f₂,f₃ and f₄ are grouped into a subband 201 for transmission to a user infrequency-selective multi-user scheduling mode. The frequency-selectivemulti-user scheduling is generally beneficial for low mobility users forwhich the channel quality can be tracked.

An example of flat and frequency-selective scheduling in an OFDM systemis shown in FIG. 4. As illustrated in FIG. 4, User 1's signal quality isbetter around the edge resource blocks RB#1, RB#2, RB#3, RB#8, RB#9,RB#10, RB#11 and RB#12, and User 2's signal quality is better around themiddle resource blocks RB#4, RB#5, RB#6 and RB#7. If User 1 is scheduledat the edge resource blocks and User 2 is scheduled at the middleresource blocks, the signal quality can be improved. The channel qualityindication (CQI) feedback per subband from a User Equipment (UE) isrequired in order to enable frequency-selective multi-user scheduling.

Multiple Input Multiple Output (MIMO) schemes use multiple transmitantennas and multiple receive antennas to improve the capacity andreliability of a wireless communication charnel. A MIMO system promiseslinear increase in capacity with K where K is the minimum of number oftransmit (M) and receive antennas (N), i.e. K=min(M,N). A simplifiedexample of a 4×4 MIMO system is shown in FIG. 5. In this example, fourdifferent data streams are transmitted separately from the fourtransmission antennas. The transmitted signals are received at the fourreception antennas. Some form of spatial signal processing is performedon the received signals in order to recover the four data streams. Anexample of spatial signal processing is vertical Bell LaboratoriesLayered Space-Time (V-BLAST) which uses the successive interferencecancellation principle to recover the transmitted data streams. Othervariants of MIMO schemes include schemes that perform some kind ofspace-time coding across the transmit antennas (e.g., diagonal BellLaboratories Layered Space-Time (D-BLAST)) and also beamforming schemessuch as Spatial Division multiple Access (SDMA).

The MIMO channel estimation consists of estimating the channel gain andphase information for links from each of the transmit antennas to eachof the receive antennas. Therefore, the channel for M×N MIMO systemconsists of an N×M matrix:

$\begin{matrix}{H = \begin{bmatrix}a_{11} & a_{12} & \ldots & a_{1M} \\a_{21} & a_{22} & \ldots & a_{2M} \\\vdots & \vdots & \ldots & \vdots \\a_{N\; 1} & a_{M\; 2} & \ldots & a_{NM}\end{bmatrix}} & (1)\end{matrix}$

where at_(ij) represents the channel gain from transmit antenna j toreceive antenna i. In order to enable the estimations of the elements ofthe MIMO channel matrix, separate pilots are transmitted from each ofthe transmit antennas.

An example of a single-code word MIMO scheme is given in FIG. 6. In caseof single-code word MIMO transmission, a cyclic redundancy check (CRC)152 is added to a single data stream 151 and then coding 153 andmodulation 154 are sequentially performed. The coded and modulatedsymbols are then demultiplexed 155 for transmission over multipleantennas 156.

In case of multiple-code word MIMO transmission, shown in FIG. 4, datastream 161 is demultiplexed 162 into smaller stream blocks. IndividualCRCs 163 are attached to these smaller stream blocks and then separatecoding164 and modulation 165 is performed on these smaller blocks. Thesesmaller blocks are then transmitted via separate MIMO antennas 166. Itshould be noted that in case of multi-code word MIMO transmissions,different modulation and coding can be used on each of the individualstreams resulting in a so called PARC (per antenna rate control) scheme.Also, multi-code word transmission allows for more efficientpost-decoding and interference cancellation because a CRC check can beperformed on each of the code words before the code word is cancelledfrom the overall signal. In this way, only correctly received code wordsare cancelled to avoid any interference propagation in the cancellationprocess.

When the transmission channels between the transmitters and thereceivers are relatively constant, it is possible to use a closed-loopMIMO scheme to further improve system performance. In a closed-loop MIMOsystem, the receiver informs the transmitter of the feedback informationregarding the channel condition. The transmitter utilizes this feedbackinformation, together with other considerations such as schedulingpriority, data and resource availability, to optimize the transmissionscheme.

A popular closed-loop MIMO scheme is MIMO precoding. With precoding, thedata streams to be transmitted are precoded, i.e., pre-multiplied by aprecoding matrix, before being passed on to the multiple transmitantennas in a transmitter.

An optional precoding protocol that employs a unitary pre-coding beforemapping the data streams to physical antennas is shown in FIGS. 8A and8B. The optional precoding creates a set of virtual antennas (VA) 171before the pre-coding. In this case, each of the codewords ispotentially transmitted through all the physical transmission antennas172. Two examples of unitary precoding matrices, P₁ and P₂ for the caseof two transmission antennas 172 may be:

$\begin{matrix}{{P_{1} = {\frac{1}{\sqrt{2}}\begin{bmatrix}1 & 1 \\1 & {- 1}\end{bmatrix}}},{P_{2} = {\frac{1}{\sqrt{2}}\begin{bmatrix}1 & 1 \\j & {- j}\end{bmatrix}}}} & (2)\end{matrix}$

Assuming modulated symbols S₁ and S₂ are transmitted at a given timethrough stream 1 and stream 2 respectively. Then the modulated symbol T₁after precoding with matrix P₁ in the example as shown in FIG. 8A andthe modulated symbol T₂ after precoding with matrix P₂ in the example asshown in FIG. 8B can be respectively written as:

$\begin{matrix}{{T_{1} = {{P_{1}\begin{bmatrix}S_{1} \\S_{2}\end{bmatrix}} = {{{\frac{1}{\sqrt{2}}\begin{bmatrix}1 & 1 \\1 & {- 1}\end{bmatrix}} \times \begin{bmatrix}S_{1} \\S_{2}\end{bmatrix}} = {\frac{1}{\sqrt{2}}\begin{bmatrix}{S_{1} + S_{2}} \\{S_{1} - S_{2}}\end{bmatrix}}}}}{T_{2} = {{P_{2}\begin{bmatrix}S_{1} \\S_{2}\end{bmatrix}} = {{{\frac{1}{\sqrt{2}}\begin{bmatrix}1 & 1 \\j & {- j}\end{bmatrix}} \times \begin{bmatrix}S_{1} \\S_{2}\end{bmatrix}} = {\frac{1}{\sqrt{2}}\begin{bmatrix}{S_{1} + S_{2}} \\{{j\; S_{1}} - {j\; S_{2}}}\end{bmatrix}}}}}} & (3)\end{matrix}$

Therefore, the symbols

$T_{11} = {{\frac{\left( {S_{1} + S_{2}} \right)}{\sqrt{2}}\mspace{14mu} {and}\mspace{14mu} T_{12}} = \frac{\left( {S_{1} - S_{2}} \right)}{\sqrt{2}}}$

will be transmitted via antenna 1 and antenna 2, respectively, whenprecoding is done using precoding matrix P₁ as shown in FIG. 8A.Similarly, the symbols

$T_{21} = {{\frac{\left( {S_{1} + S_{2}} \right)}{\sqrt{2}}\mspace{14mu} {and}\mspace{14mu} T_{22}} = \frac{\left( {{j\; S_{1}} - {j\; S_{2}}} \right)}{\sqrt{2}}}$

will be transmitted via antenna 1 and antenna 2, respectively, whenprecoding is done using precoding matrix P₂ as shown in FIG. 8B. Itshould be noted that precoding is done on an OFDM subcarrier levelbefore the IFFT operation as illustrated in FIGS. 8A and 8B.

An example of MIMO precoding is Fourier-based precoding. A Fouriermatrix is a N×N square matrix with entries given by:

P _(N) =e ^(j2πmn/N) m,n=0,1, . . . (N−1)   (4)

A 2×2 Fourier matrix can be expressed as:

$\begin{matrix}{P_{2} = {\begin{bmatrix}1 & 1 \\1 & ^{j\pi}\end{bmatrix} = \begin{bmatrix}1 & 1 \\1 & {- 1}\end{bmatrix}}} & (5)\end{matrix}$

Similarly, a 4×4 Fourier matrix can be expressed as:

$\begin{matrix}{P_{4} = {\begin{bmatrix}1 & 1 & 1 & 1 \\1 & ^{{j\pi}/2} & ^{j\pi} & ^{{j3\pi}/2} \\1 & ^{j\pi} & ^{j2\pi} & ^{j3\pi} \\1 & ^{{j3\pi}/2} & ^{j3\pi} & ^{{j9\pi}/2}\end{bmatrix} = \begin{bmatrix}1 & 1 & 1 & 1 \\1 & j & {- 1} & {- j} \\1 & {- 1} & 1 & {- 1} \\1 & {- j} & {- 1} & j\end{bmatrix}}} & (6)\end{matrix}$

Multiple precoder matrices can be defined by introducing a shiftparameter (g/G) in the Fourier matrix as given by:

$\begin{matrix}{{P_{mn} = {^{\frac{j\; 2\pi \; m}{N}{({n + \frac{g}{G}})}}\mspace{14mu} m}},{n = 0},1,{\ldots \mspace{14mu} \left( {N - 1} \right)}} & (7)\end{matrix}$

A set of four 2×2 Fourier matrices can be defined by taking G=4. Thesefour 2×2 matrices with g=0, 1, 2 and 3 are written as:

$\begin{matrix}{P_{2}^{0} = \begin{bmatrix}1 & 1 \\1 & {- 1}\end{bmatrix}} & (8) \\{P_{2}^{1} = \begin{bmatrix}1 & 1 \\^{{j\pi}/4} & {- ^{{j\pi}/4}}\end{bmatrix}} & (9) \\{P_{2}^{2} = \begin{bmatrix}1 & 1 \\^{{j\pi}/2} & {- ^{{j\pi}/2}}\end{bmatrix}} & (10) \\{P_{2}^{3} = \begin{bmatrix}1 & 1 \\^{{j3\pi}/4} & {- ^{{j3\pi}/4}}\end{bmatrix}} & (11)\end{matrix}$

In a transmission path from a base station to a user equipment (UE),i.e., downlink transmission, the precoding matrix is usually determinedin dependence upon a precoding feedback information that is transmittedby the user equipment to the base station. The precoding feedbackinformation typically includes precoding-matrix identity.

When the total bandwidth in an OFDM system is divided into a pluralityof subbands, each subband being a set of consecutive subcarriers, due tofrequency-selective fading in the OFDM system, the optimal precoding fordifferent subbands (SBs), can be different, as shown in one exampleillustrated in FIG. 9. In FIG. 9, different SBs use different precodingmatrix. Subband 1 (SB1) which includes continuous OFDM subcarriers 1through 64, uses precoding matrix P₂ ²; SB2 which includes continuousOFDM subcarriers 65 through 128, uses precoding matrix P₂ ¹, etc.Therefore, the precoding feedback information is transmitted on asubband basis. Moreover, due to feedback errors, the base station alsoneeds to inform the user equipment of the precoding information used ontransmitted subbands. This results in additional signaling overhead inthe downlink.

Besides precoding information, another form of feedback information isrank information, i.e., the number of MIMO layers. A MIMO layer is aspatial channel that can carry data symbols. It is well known that evenwhen a system can support 4×4 MIMO, rank-4 (4 MIMO layers) transmissionsare not always desirable. The MIMO channel experienced by the UEgenerally limits the maximum rank that can be used for transmission. Ingeneral for weak users in the system, a lower rank transmission ispreferred over a higher rank transmission from the throughputperspective. Moreover, due to frequency-selective fading, optimal rankmay be different on different subbands. As shown in the example of FIG.10, SB1 uses rank-1 transmission; SB2 uses rank-2 transmission, etc.Therefore, the UE needs to include the rank information in the feedbackinformation on a subband basis. Also, due to a possibility of feedbackerrors, the base station additionally needs to indicate the transmittedMIMO rank on different subbands. The rank information can also be commonacross the subbands, that is, a single rank value is reported for allthe subbands. In any case, this results in additional overhead on thedownlink.

Still another form of MIMO feedback information is layer orderinginformation. In the example of FIG. 11, the layer order for SB1, SB2,SB4, SB5 and SB8 is layer 2, and then layer 1; while the layer order forSB3, SB6 and SB7 is layer 1, and then layer 2. The layer orderinginformation is generally transmitted by the UE and also indicated by thebase station in control signaling on the downlink. The ordering oflayers can be based on the channel quality they experience or othersimilar criteria.

Another form of MIMO feedback information which applies to both MIMO andnon-MIMO scenarios is the selected subbands for transmission. In thiscase, the MIMO feedback information such as preceding, rank, IDs ofselected layers and layer ordering is provided for the selected subbandsonly. In this case, however, both the UE and the base station need tosignal the information on the selected subbands.

The Physical Uplink Control Channel (PUCCH) in the LTE system usuallyuses CAZAC Zadoff-Chu (ZC) sequence. A Zadoff-Chu (ZC) sequence oflength Nis defined as

$\begin{matrix}{{g_{p}(n)} = \left\{ {{{\begin{matrix}^{{- j}\frac{2\pi \; 1}{M\; 2}{pn}^{2}} & {{when}\mspace{14mu} N\mspace{14mu} {is}\mspace{14mu} {even}} \\^{{- j}\frac{2\pi \; 1}{M\; 2}{{pn}{({n + 1})}}} & {{{when}\mspace{14mu} N\mspace{14mu} {is}\mspace{14mu} {odd}},}\end{matrix}n} = 0},1,\ldots \mspace{14mu},{N - 1}} \right.} & (12)\end{matrix}$

where p, the sequence index, is relatively prime to N (i.e. the onlycommon divisor for p and Nis 1). For a fixed p, the Zadoff-Chu (ZC)sequence has ideal periodic auto-correlation property (i.e. the periodicauto-correlation is zero for all time shift other than zero). Fordifferent p, ZC sequences are not orthogonal, but exhibit low crosscorrelation. If the sequence length N is selected as a prime number,there are N−1 different sequences with periodic cross-correlation of1/√{square root over (N)} between any two sequences regardless of timeshift.

In summary, with Zadoff-Chu sequence, N−1 different sequences with fixedperiodic cross-correlation are available to be used as preambles,provided that N is a prime number. In addition, each of the sequence hasideal periodic auto-correlation property.

Single carrier frequency division multiple access (SC-FDMA), whichutilizes single carrier modulation and frequency domain equalization isa technique that has similar performance and complexity as those of anOFDMA system. One advantage of SC-FDMA is that the SC-FDMA signal haslower peak-to-average power ratio (PAPR) because of its inherent singlecarrier structure. Low PAPR normally results in high efficiency of poweramplifier, which is particularly important for mobile stations in uplinktransmission. SC-FDMA is selected as the uplink multiple acess scheme in3GPP long term evolution (LTE). An example of the transceiver chain forSC-FDMA is shown in FIG. 12. At the transmitter side, the data orcontrol signal is serial to parallel (S/P) converted by a S/P convertor181. Discrete Fourier transform (DFT) will be applied to time-domaindata or control signal by a DFT transmformer 182 before the time-domaindata is mapped to a set of sub-carriers by a sub-carrier mapping unit183. To ensure low PAPR, normally the DFT output in the frequency domainwill be mapped to a set of contiguous sub-carriers. Then IFFT, normallywith larger size than the DFT, will be applied by an IFFT transformer184 to tranform the signal back to time domain. After parallel to serial(P/S) convertion by a P/S/converter 185, cyclic prefix (CP) will beadded by a CP insertion unit 186 to the data or the control signalbefore the data or the control signal is transmitted to a transmissionfront end processing unit 187. The processed signal with a cyclic prefixadded is often referred to as a SC-FDMA block. After the signal passesthrough a communication channel 188, e.g., a multipath fading channel ina wireless communication system, the receiver will perform receiverfront end processing by a receiver front end processing unit 191, removethe CP by a CP removal unit 192, apply FFT by a FFT transformer 194 andfrequency domain equalization. Inverse Discrete Fourier transform (IDFT)196 will be applied after the equalized signal is demapped 195 infrequency domain. The output of IDFT will be passed for furthertime-domain processing such as demodulation and decoding.

An example of resource allocation for PUCCH in a LTE SC-FDMA system, isshown in FIG. 13. Resources at the edge of a band are allocated tocontrol channel. Each resource channel for uplink control will hop fromone edge of the band to the other edge of the band across the two slotswithin a subframe to capture frequency diversity while preserving thesingle-carrier transmission property, because the mobile station onlytransmit within a contiguous frequency band at any given time.Acknowledgement (ACK) channel is transmitted on one of these resourcechannels in the case there is no uplink data transmission. In the casewhen there is uplink data transmission, ACK and other uplink controlchannels can be multiplexed with the data transmission within theresource blocks assigned to that mobile station.

The different types of feedback information from the UE are summarizedas below:

Subbands CQI Information

MIMO Rank

Antenna/Layer selection

MIMO Frecoding

ACK/NACK for downlink data transmission

In the contemporary transmission schemes, each type of feedback controlinformation is separately coded/modulated and transmitted. This resultsin inefficient transmission because efficient coding across multiplecontrol types cannot be employed. Moreover, if some type of CRC is usedfor error detection purpose, separate CRCs are required for each of thecontrol information types resulting in excessive overhead.

In this invention, we describe a scheme to jointly code different typesof feedback information from the UE as shown in FIG. 14. The Formatfield indicates the length of each field and whether a given field ispresent or not. For example, ACK/NACK feedback may only present ifdownlink transmission from the base station was received and an ACK or aNACK message needs to be transmitted at the time of transmission of thefeedback control message. Similarly, in some cases one feedbackinformation changes more than the other. In this case, it is appropriateto feedback the information that has experiences a larger delta change.For example, in some cases, CQI information can be updated whileproviding no information on MIMO precoding. At other instances, MIMOprecoding information can be provided while not updating the CQIinformation. Note the message fields shown in FIG. 14 are forillustration purpose. This invention certainly covers schemes thatjointly encodes a subset of fields shown in FIG. 14, and schemes thatjointly encodes multiple message fields that may include fields notshown in FIG. 14.

When different types of information is coded together, it is alsopossible to transmit the control information more efficiently. As shownin FIG. 15, rank and selected layers information is combined into asingle field. A total of 4-bits feedback (4+6+4+1=15 combinations) isprovided for MIMO rank and layer selection indication for the case of 4transmission antennas (antennas 1, 2, 3 and 4) MIMO transmission.Specifically, four combinations (combinations 0 through 3) are providedfor Rank-1 transmission; six combinations (combination 4 through 9) areprovided for Rank-2 transmission; four combinations (combination 10through 13) are provided for Rank-3 transmission; and one combination(combination 14) is provided for Rank-4 transmission. In case of twotransmission antennas, MIMO rank and layer selection indication requiresonly 2-bits.

According to a first embodiment of the principles of the presentinvention, Table 1 lists eleven possible physical uplink control channel(PUCCH) formats. The PUCCH may contain seven fields: “Format”, “SubbandsCQI”, “MIMO rank and selected layers”, “MIMO precoding”, “ACK/ACK”,“Reserved” and “CRC”. The PUCCH may have a total of five possiblepayload sizes, namely 60, 43, 36, 27 and 16 bits. We assume that the UEprovides feedback when one (1), five (5) or ten (10) subbands over thetotal bandwidth are defined. The first possible control channel, i.e.,control channel 1 carries subband CQI and subband based MIMO precodinginformation for the case of 10 subbands. The total payload size forcontrol channel 1 is 60 bits. Control channel 2 carries subband CQI butno MIMO information for the case of 10 subbands. If we assume that MIMOrank information is common across the subbands, it is not necessary forthe PUCCH to carry the information about the MIMO rank and the selectedlayers. Therefore, the number of bits in the field of “MIMO rank andselected layers” may be zero (0). The payload size for control channel 2is 36 bits. Control channel 3 carries MIMO information for the case of10 subbands but no CQI information. The payload size for control channel3 is 36 bits. A UE may transmit control channel 2 and control channel 3alternatively to provide the Node-B (i.e., the base station) informationon both subband CQI and subband-based precoding. A 1-bit Formatindication tells the Node-B which information is carried at a giventime. This alternative transmission of control channel 2 and controlchannel 3 allows UE to transmit at a lower power compared to the casewhere UE uses control channel 1 for transmission of both subband CQI andsubband precoding information. The Node-B does not need to blindlydecode between control channel 2 and control channel 3 because of thepresence of 1-bit format indication.

Control channel 4 is used when UE feedbacks subband CQI with common MIMOpercoding information for the case of 10 subbands. Control channel 7with the same payload size (i.e., 43 bits) is used when UE feedbackssubband CQI and also subband-based MIMO precoding MIMO information forthe case of 5 subbands. A 1-bit format indicator differentiates betweenchannel number 4 and 7.

Control channels 5, 6, 8 and 9 have the same 27 bits payload size andare differentiated by a 2-bit format indicator field. Control channel 5,for example, is used when UE feedbacks average CQI and common precodingwhich is effectively a single subband case.

The remaining 2 control channels namely control channel 10 and controlchannel 11 are used for average CQI feedback and no MIMO precoding. Thedifference between control channel number 10 and 11 is that 10 does notcarry an ACK/NACK field. The channel number 11 carries a 2-bit ACK/NACKfiled and a reduced granularity 3-bit CQI field. Both the controlchannel carries a total of 16 bits.

In other embodiments not described here, another PUCCH format carryingaverage CQI and subband precoding can be defined. It is also possible toadd other fields in the PUCCH such as uplink resource requests, thuscreating additional control formats. Also, when ACK/NACK is notexpected, the 2-bits ACK/NACK field can be used for other purposes suchas sending resource requests etc. Similarly, when two transmissionantennas MIMO is used, MIMO rank and layer selection field only requires2-bits and therefore the remaining 2-bits can be used for other types ofuplink feedback or making more bits available to some of the fields suchas CQI field.

TABLE I Uplink PUCCH control channel formats MIMO Control Rank andchannel Subbands selected MIMO ACK/ Total No. Format CQI LayersPrecoding NACK Reserved CRC bits Subband CQI and 1 0 25 4 20 2 1 8 60Subband precoding [10 subbands] Suband CQI and no 2 1 25 0 0 2 0 8 36MIMO information [10 subbands] MIMO and 3 1 0 4 20 2 1 8 36 ACK/NACK(No- CQI information) [10 subbands] Suband CQI and 4 1 25 4 3 2 0 8 43Common precoding [10 subbands] Average CQI and 5 2 5 4 3 2 3 8 27 commonprecoding [1 subband] Average CQI and no 6 2 5 4 0 2 6 8 27 (fixed)precoding [1 subband] Suband CQI and 7 1 15 4 10 2 3 8 43 Subbandprecoding [5subbands] Suband CQI and no 8 2 15 0 0 2 0 8 27 MIMOinformation [5 subbands] MIMO and 9 2 0 4 10 2 1 8 27 ACK/NACK (No- CQIinformation) [5- subbands] Average CQI, no 10 1 5 2 0 0 0 8 16 (fixed)precoding, no ACK/NACK Average CQI (3-bits 11 1 3 2 0 2 0 8 16 reducedgranularity), no precoding, 2-bits ACK/NACK

In a second embodiment according to the principles of the presentinvention, as shown in FIG. 16, the PUCCH is first transferred into tailbit insertion unit 210. Tails bits are a fixed sequence of bits added tothe end of a block of data to reset convolutional encoder 212 to apredefined state. Then, the PUCCH is coded with a convolutional code byconvolutional encoder 212. The coded information is punctured asnecessary by Puncturing/Repetition unit 214. After S/P conversion by S/Pconversion unit 216, the information is modulated by modulator 218 usingQuadrature Phase-Shift Keying (QPSK) modulation. A Constant AmplitudeZero Autocorrelation (CAZAC) sequence modulator 220 further modulatesthe complex modulated symbols using a CAZAC sequence. CAZAC sequence isused as an example and modulation with other sequences is also possible.An FFT operation is performed by FFT transformer 222 on the modulatedCAZAC sequence and the resulting samples are mapped by mapping unit 224to the PUCCH subcarrier resources at the input of IFFT 226. Afteraddition of the cyclic prefix, the resulting signal is unconverted to RFby an upconversion unit . 228 and transmitted via at least one antenna.It should be noted that other modulation formats other than QPSK such asBinary Phase Shift Keying (BPSK) and 16-Quadrature Amplitude Modulation(QAM) can be used. Moreover, coding schemes other than convolutionalcoding, such as tail-biting convolutional codes or various types ofblock codes can be used. Also, one or more steps in the process can beskipped. For example, in some embodiments, the modulated symbols can bedirectly FFT precoded and mapped to physical resource without the needfor CAZAC sequence modulation. In another embodiment, the FFT precodingoperation can be skipped, for example.

In an example embodiment according to the principles of the presentinvention shown in FIG. 17, 8 tail bits are added to 36-bits of PUCCHinformation and the information is convolutional coded with a ⅓ codingrate. This results in a total of 132 coded bits. In the next step, 36bits are punctured providing 96 coded bits. These 96 bits are QPSKmodulated resulting in 48 complex modulated symbols. Each complexmodulated symbol further modulates a CAZAC sequence and the resulting 48sequences are mapped to 48 physical resource elements.

According to a third embodiment of the principles of the presentinvention, an example of PUCCH physical resource mapping is shown inFIG. 18. In the third embodiment of the present invention, a coherentmodulation using QPSK is assumed. As shown in FIG. 19, in the case ofcoherent transmission, the CAZAC sequence is modulated with themodulated symbols and pilot or reference signals are transmitted to aidchannel estimation at the receiver. In the case of coherent reception,the channel estimation is performed based on the received pilot orreference signals. The channel estimates are then used to performfrequency-domain equalization (FDE) of the received PUCCH data symbols.The equalized modulated samples at the output of FDE are demodulated bythe used CAZAC sequence to obtain the transmitted PUCCH data modulatedsymbols. In coherent modulation using QPSK, two bits can be carried by asingle sequence. Regarding the mapping of the PUCCH, a resource element(RE) is defined as one RB over a single SC-FDMA block or OFDM symbol. Inthe example of FIG. 18, the PUCCH is mapped to forty-eight (48) REs,that is, the PUCCH is transmitted over four (4) RBs in twelve (12)SC-FDMA blocks. Each QPSK symbol modulates a length twelve (12) CAZACsequence and each modulated CAZAC sequence is mapped to one RE (12subcarriers).

In a fourth embodiment according to the principles of the presentinvention shown in FIG. 20, the PUCCH is mapped to four subframes withone RB used in each subframe. Each CAZAC sequence is of a length of 12and is mapped to 12 subcarriers. There are 12 SC-FDMA blocks within asubframe. Therefore, 12 CAZAC sequences are carried within a subframe.Each subframe carries tweleve modulated CAZAC sequences with foursubframes carrying forty-eight modulated CAZAC sequences. This allowsfor exploiting some time-diversity in the transmission of PUCCH. Also,for smaller bandwidths the total number of RBs is small and thereforespreading the PUCCH in time allows using smaller number of RBs persubframe.

In a fifth embodiment according to the principles of the presentinvention, different length CAZAC sequences can be used. For example,FIG. 21 shows the case where length 6 CAZAC sequences are used. In thiscase, total of 48 modulated CAZAC sequences are transmitted over 2resource blocks (RBs), that is over 24 resource elements. In this caseeach resource element containing 12 subcarriers contain 2 CAZACsequences of length 6 each.

In a sixth embodiment according to the principles of the presentinvention shown in FIG. 22, the PUCCH is mapped to 4 subcarriers in 12SC-FDMA blocks without CAZAC sequence modulation. The 4 subcarriers in12 SC-FDMA blocks provide 48 subcarriers that are used to carry 48 QPSKmodulated symbols from PUCCH.

In a seventh embodiment according to the principles of the presentinvention shown in FIG. 23, multiple length 256 CAZAC sequences, i.e.,256 possible CAZAC sequences are transmitted over two hundred andfifty-six (256) subcarriers in twelve SC-FDMA blocks. Each of the 256possible CAZAC sequences has 256 elements. Unlike the previousembodiments, the seventh embodiment uses a non-coherent transmission. Asshown in FIG. 24, in the case of non-coherent transmission, the CAZACsequence is mapped to the subcarriers at the input of IFFT. WhenFFT-precoding is used, the CAZAC sequence is mapped at the input of FFTand the samples at the output of FFT are mapped to subcarriers at theinput of IFFT. In case of non-coherent reception, the receiver performsa correlation operation on the received frequency domain samples withall the possible CAZAC sequences expected. Then a decision is made onthe received CAZAC sequence based on a threshold criterion. Since asingle sequence . from among multiple possible sequences is received,the received sequence indicates the information bits of PUCCH. Each ofthe 256 possible CAZAC sequences can be represented by 8-bitsinformation because 2⁸=256. Among the 256 CAZAC sequences, a singlesequence is selected to be transmitted in each of the twelve SC-FDMAblocks. This allows carrying 8-bits in each SC-FDMA block with a totalof 96 coded bits in these twelve SC-FDMA blocks (12×8=96). It should benoted that in this case a non-coherent detection can be performed on thetransmitted sequences without requiring pilot or reference signalstransmitted with PUCCH.

In a seventh embodiment according to the principles of the presentinvention shown in FIG. 25, two length-16 CAZAC sequences, i.e., sixteenpossible CAZAC sequences, are transmitted over thirty-two subcarriers ineach of the twelve (12) SC-FDMA blocks. Among the sixteen CAZACsequences, a single sequence is transmitted using 16 sub-carriers ineach SC-FDMA block. This allows carrying 4 bits in each 16 sub-carriersin each SC-FDMA block. Therefore, a total of 96 coded bits can becarried in 32-subcarriers in the 12 SC-FDMA blocks (12×2×4=96). Itshould be noted that in this case a non-coherent detection can beperformed on the transmitted sequences without requiring pilot orreference signals transmitted with PUCCH.

Base station, also referred to as eNode-B in the LTE system, canconfigure what PUCCH channel a UE can use. In case eNode-B allows a UEto use all the possible PUCCH formats listed in Table-I, a total of fiveblind decodings for the 5 payload sizes are necessary at the eNode-B. Atotal of eleven different PUCCH actual formats are supported, however,and some of the formats are differentiated using the 1 or 2-bit Formatfield and hence do not require additional blind decodings.

It should be noted that when ACK/NACK is transmitted jointly coded withother information, upon CRC failure, eNode-B should interpret anyACKINACK transmitted at that time as a NACK signal.

In cases where additional SC-FDMA blocks are used for other purposessuch as sounding reference signal (RS), additional puncturing of codedsymbols may be performed or a larger number of RBs or subcarriers can beallocated to PUCCH.

1.-26. (canceled)
 27. A method for transmitting control information, themethod comprising: receiving a reference signal from a firsttransceiver; in response to the reception of the reference signal,determining a plurality of control information based upon the receivedreference signal; jointly encoding the plurality of control informationusing a block code; modulating the encoded control information togenerate a plurality of modulated symbols using a selected modulationscheme; multiplying a selected sequence with the modulated symbols togenerate a plurality of multiplied sequences; mapping the plurality ofmultiplied sequences into two sets of resource elements in time andfrequency domains in a subframe, a first set of the two sets of resourceelements being located in one edge of the subframe in the frequencydomain and in a first half of the subframe in the time domain, and asecond set of the two sets of resource elements being located in anopposite edge of the subframe in the frequency domain and in a secondhalf of the subframe in the time domain; and converting the mappedsequences to radio frequency signals for transmission.
 28. The method ofclaim 27, further comprising: mapping the plurality of multipliedsequences into the two sets of resource elements with each element of amultiplied sequence corresponding to one resource element.
 29. Themethod of claim 27, further comprising selecting a subset of multipliedsequences to be mapped into the first set of the two sets of resourceelements, wherein the multiplied sequences within the subset ofmultiplied sequences are mapped into the first set of the two sets ofresource elements with each element of a multiplied sequencecorresponding to one resource element.
 30. The method of claim 27,wherein each resource element is formed with one subcarrier.
 31. Themethod of claim 27, further comprising: identifying availabletransmission resources comprising a plurality of equal duration resourceelements.
 32. An apparatus configured to communicate controlinformation, the apparatus comprising: a receiver configured to receivea reference signal from a transceiver; and a controller configured to:determine, in response to reception of the reference signal, a pluralityof control information based upon the received reference signal; jointlyencode the plurality of control information using a block code; modulatethe encoded control information to generate a plurality of modulatedsymbols using a selected modulation scheme; multiply a selected sequencewith the modulated symbols to generate a plurality of multipliedsequences; map the plurality of multiplied sequences into two sets ofresource elements in time and frequency domains in a subframe, with afirst set of the two sets of resource elements being located in one edgeof the subframe in the frequency domain and in a first half of thesubframe in the time domain, and a second set of the two sets ofresource elements being located in an opposite edge of the subframe inthe frequency domain and in a second half of the subframe in the timedomain; and convert the mapped sequences to radio frequency signals fortransmission.
 33. The apparatus of claim 31, wherein the controller isfurther configured to map the plurality of multiplied sequences into thetwo sets of resource elements with each element of multiplied sequencecorresponding to one resource element.
 34. The apparatus of claim 31,wherein the controller is further configured to select a subset ofmultiplied sequences to be mapped into the first set of the two sets ofresource elements, wherein the multiplied sequences within the subset ofmultiplied sequences are mapped into the first set of the two sets ofresource elements with each element of a multiplied sequencecorresponding to one resource element.
 35. The apparatus of claim 31,wherein each resource element is formed with one subcarriers.
 36. Theapparatus of claim 31, wherein the controller is further configured toidentify available transmission resources comprising a plurality ofequal duration resource elements.
 37. An apparatus configured to receivecontrol information, the apparatus comprising: a transmitter configuredto transmit a reference signal to a transceiver; and a receiverconfigured to receive a control signal from the transceiver, wherein thecontrol signal is generated by: in response to the reception of thereference signal, determining a plurality of control information basedupon the received reference signal; jointly encoding the plurality ofcontrol information using a block code; modulating the encoded controlinformation to generate a plurality of modulated symbols using aselected modulation scheme; multiplying a selected sequence with themodulated symbols to generate a plurality of multiplied sequences;mapping the plurality of multiplied sequences into two sets of resourceelements in time and frequency domains in a subframe, with a first setof the two sets of resource elements being located in one edge of thesubframe in the frequency domain and in a first half of the subframe inthe time domain, and a second set of the two sets of resource elementsbeing located in an opposite edge of the subframe in the frequencydomain and in a second half of the subframe in the time domain; andconverting the mapped sequences to radio frequency signals fortransmission.
 38. The apparatus of claim 37, wherein the control signalis generated by: mapping the plurality of multiplied sequences into thetwo sets of resource elements with each element of a multiplied sequencecorresponding to one resource element.
 39. The apparatus of claim 37,wherein the control signal is generated by selecting a subset ofmultiplied sequences to be mapped into the first set of the two sets ofresource elements, wherein the multiplied sequences within the subset ofmultiplied sequences are mapped into the first set of the two sets ofresource elements with each element of a multiplied sequencecorresponding to one resource element.
 40. The apparatus of claim 37,wherein each resource element is formed with one subcarriers.
 41. Theapparatus of claim 37, wherein the control signal is generated byidentifying available transmission resources comprising a plurality ofequal duration resource elements.